Conventionally, there have been known centrifugal blowers including a scroll casing and a multiblade type centrifugal fan. In the centrifugal blower, noise called wind noise occurs due to pressure change when blades of the fan pass in the vicinity of a tongue portion provided in the scroll casing. Thus, in a centrifugal blower disclosed in Patent Reference 1, the tongue portion is configured stepwise so that a distance between the tongue portion and the fan is larger on a main plate side of the fan than on a side plate side (an intake side) of the fan.